Sexual Selection Mechanisms

Study Notes

Intrasexual Competition

Darwin proposed two mechanisms for sexual selection, the first being intrasexual competition.
Intrasexual competition occurs when individuals of the same sex compete for access to mates.
A classic example involves stags battling for dominance.
Winners gain mating access, either directly or through controlling resources desired by females.
Losers typically fail to reproduce.
Traits linked to success in intrasexual competition are passed on, while those linked to losing are not.
This drives evolutionary changes over time.

Intersexual Selection

The second mechanism is intersexual selection, also known as preferential mate choice.
In this process, one sex exhibits preferences for specific traits in the opposite sex.
Individuals with desired traits are preferentially chosen as mates.
Those lacking these traits often mate less frequently or not at all.
This leads to an increase in the frequency of desirable traits over generations.
Darwin termed this process "female choice," observing that females often demonstrate greater selectivity in mate selection than males.
An example includes females favoring males who offer food gifts, leading to an increase in males adept at acquiring such gifts.

Misunderstanding 1: Human Behavior is Genetically Determined

Evolutionary theory suggests that human behavior requires both evolved adaptations and environmental input.
This theory doesn't support genetic determinism, which claims behavior is solely controlled by genes.
Adaptations evolve to help organisms cope with environmental challenges.
Genetic determinism is incorrect and not implied by evolutionary theory.

Misunderstanding 2: If It Is Evolutionary, We Cannot Change It

Understanding our evolved social psychology and the social inputs that activate it can empower us to change behavior.
Knowledge of mechanisms facilitates change, rather than preventing it.
While changing behavior might be complex, knowledge of our evolved psychology can help us change in desired areas.

Misunderstanding 3: Current Mechanisms Are Optimally Designed

The current human adaptations aren't designed perfectly. Two factors contribute to this:
- Evolutionary time lags: We are adapted to past environments, leading to mismatches in today's world.
- Costs of adaptations: Adaptations can have drawbacks, and natural selection favors mechanisms that balance benefits and costs.
The "Stone Age brain" in a modern environment highlights how our adaptations may not be suited for current conditions.
Costs of adaptations (e.g., fear of snakes/spiders) can hinder other survival needs, preventing optimal design. Adaptations are reasonably good, but not perfectly designed due to cost constraints.

Description

Explore the two mechanisms of sexual selection: intrasexual competition and intersexual selection. Understand how these processes shape mating behaviors and influence evolutionary changes over generations. Discover classic examples and the importance of traits linked to reproductive success.